System.getenv()和System.getProperty()之间的区别

Question

可能重复:
System属性和环境变量之间的区别是什么

System.getenv()和System.getProperty()有什么区别？

当我们使用Processbuilder运行任何命令时,我们可以设置环境变量,即:

String[] vCmd = { System.getenv("ANT_HOME") + "/bin/ant", "-f",
                ANT_BUILD_FILE, TARGET };
        ProcessBuilder pb = new ProcessBuilder(vCmd);
        Map<String, String> env = pb.environment();     
        env.put("CLASSPATH",
                antHome+"/lib/ant.jar:"
                        + antHome+"/lib/ant-launcher.jar:"
                        + antHome+"/lib/ant-nodeps.jar:"
                        );
        try{

            Process process = pb.start();
            InputStream is = process.getInputStream();
            InputStreamReader isr = new InputStreamReader(is);
            BufferedReader br = new BufferedReader(isr);
            String line;
            while ((line = br.readLine()) != null) {
                System.out.println(line);
            }
            pb.wait();
        }
        catch(Exception e)

            System.out.println(e.getMessage());


        }

如果我在此方法之前使用System.setProperties()设置了一些属性,那么ProcessBuilder启动此进程是否可用？

Answer 1

getenv获取环境变量.getProperty获取Java属性.环境变量在OS级别指定.通过将-D选项传递给JVM 来指定Java属性(并且可以通过编程方式设置).

Answer 2

System.getenv()适用于操作系统环境变量,而System.getProperty()适用于传递-DpropName=value给Java应用程序启动器(java)的JVM参数.